Referring to FIGS. 1 and 2, U.S. Pat. No. 6,951,632 B2 discloses a microfluidic device 1 and a manufacturing method thereof.
The microfluidic device 1 is made by a conventional multilayer soft lithography (MSL) process. Specifically, the manufacturing method of the microfluidic device 1 includes: placing a capillary element 11 in contact with and perpendicular to a protrusion 100 of a mold 10; coating an elastomeric polymer precursor 12 on the mold 10 and surrounding the capillary element 11; removing the mold 10 from the elastomeric polymer precursor 12, such that the elastomeric polymer precursor 12 is formed with a micro-trench 120 that is complementary in shape to the protrusion 100 of the mold 10 and that is in spatial communication with the capillary element 11; attaching an elastic thin membrane layer 13 to the elastomeric polymer precursor 12 to cover the micro-trench 120, such that a microfluidic channel 121 is formed; and attaching a control channel layer 14 to the elastic thin membrane layer 13, the control channel layer 14 having a control channel 141 that faces the elastic thin membrane layer 13 and that is transverse to the microfluidic channel 121.
The capillary element 11 is used for injecting fluid into the microfluidic channel 121 or dispensing fluid from the microfluidic channel 121. When the microfluidic device 1 is in operation, a pressurized gas is introduced into the control channel 141 to deform the elastic thin membrane layer 13 to close the microfluidic channel 121, thereby cutting off fluid passage in the microfluidic channel 121 (see right side of FIG. 2). When the pressurized gas is discharged from the control channel 141, the elastic thin membrane layer 13 is returned to its undeformed state, allowing fluid passage in the microfluidic channel 121 (see left side of FIG. 2).
The MSL process suffers a misalignment issue while attempting to attach the control channel layer 14 onto the elastic thin membrane layer 13, in which the control channel 141 may not be precisely positioned to intersect with the microfluidic channel 121, thereby causing the microfluidic channel 121 to be inaccurately closed.